For anyone interested, had the TDV8 "remapped" and a new larger exhaust fitted at Roo Systems in Brisbane. Dyno graphs attached. I chose the most conservative tune, so ended up with a few more HP (around an extra 40kw)and around 150 extra torqs as Mr Clarkson would say. TBH the best part is a magnificent exhaust note under "brisk" acceleration - no noise change at cruise or "normal" throttle position so its still quiet as a mouse on the freeway - until you choose to blast passed something.

Full details on Roo Systems website if you want to know more; price, EGT temps, warranty etc etc - suggest you just call them - they were very good to deal with.